refs https://github.com/TryGhost/Ghost/issues/10922
- adds migrations to...
1. add `post.type` column
2. populate `post.type` column based on `post.page` value
3. drop `post.page` column
- updates all code paths to work with `post.type` in place of `post.page`
- adds `nql-map-key-values` transformer for mapping `page`->`type` in `filter` params when using the v2 API
- modifies importer to handle `post.page`->`post.type` transformation when importing older export files
no issue
- Session controllers were using API v1 http method which bypassed "frame" introduced with API v2.
- Changes here are just a long-awaited cleanup to allow completely remove v0.1 code
